The present invention relates to a structure of an ignition device for an internal combustion engine.
Conventional methods for suppressing an induced voltage generated at a lower-voltage end of a secondary winding of an ignition coil at a primary current supply timing include a method using a high-voltage diode connected to a higher-voltage end of the secondary winding as described in Japanese Patent Laid-open No. 55-66659 and a method using a Zener diode connected to a lower-voltage end of the secondary winding, the Zener diode coming into conduction at a reverse voltage higher than the induced voltage generated at the lower-voltage end of the secondary winding as described in Japanese Patent Publication No. 6-94864. In each method, the diode used has a breakdown voltage higher than the induced voltage generated at the lower-voltage end of the secondary winding at the primary current supply timing. Accordingly, the diode is configured by using an element having a high withstand voltage.
In the prior art mentioned above, the use of the diode having a breakdown voltage higher than the induced voltage generated at the lower-voltage end of the secondary winding at the primary current supply timing requires an element having a high withstand voltage. However, such a diode having a high withstand voltage is expensive and bulky, causing a disadvantage in view of cost and space.